At this time my new Techtonic Tuning 304 Stainless Steel mandrel bent 2.5" cat back exhaust system with straight through Borla muffler is making its way across the county from Oregon to Florida. Total cost with shipping was $529. This system is NOT what your local Midas muffler shop could provide since not many exhaust people have a mandrel bending machine.

The same setup in aluminized steel sells for about $306, since I am in Florida and we do have alot of salt in the air, I went with the stainless steel system for longetivity.

This installation should assist the Garrett VNT15 spool up quicker and create significantly less backpressure, especially when my peak boost is finally increased. With the Wetterauer software, K&N cone filter, and no MAF screens I am looking for a total increase in power of about 30% giving me 120HP and 200 lb of torque. Next step will be increased turbo boost pressure for even more power to my final goal of 150HP and 250 lbs of torque, which only increased intake air flow and increased exhaust flow could possibly provide.

BTW, the same system from Techtonics for the NB has an outrageous STINGER tip that sticks up just like on the exhaust extrctor systems on the air-cooled hoped up Bugs. Really a sweet looking set-up!

Did I tell you of my resonator removal?
On my '98 Jetta TDI w/Techtonics cat-back
system (aluminized 2 1/2" w/ Borla stainless
muffler), I had my friendly Meineke remove the resonator a week ago, and got to inspect
it closely while up on the hoist.

The downpipe actually looks decent, at approximately 2 1/2", but where it connects
to the stupid cat it necks down to 2", then
post-cat, back up to 2 1/2" for the TT front
pipe. The cat appears to be the definite
"fly in the ointment" here. I've heard
(maybe you can confirm this) that there is no legal requirement for a catalytic convertor
on a diesel. My brother's old diesel Rabbit
had none...

Nevertheless, I can't get Meineke to touch it. Short of a 2,200+ mile trek to
Sheridan, Oregon, to volunteer my car as
a testbed for Techtonics, any suggestions?
I'm dreaming of a cat-free 3" mandrel-bent
headpipe-back system with just a "back-box",
as the Brits call it. Maybe a Remus with dual tips....

BTW, the resonator removal is beneficial, as
the deep throaty sound of exhaust, as opposed
to drivetrain noise, is more prominent. Just
a hair smoother accelerating, as far as I can tell.

I am not sure if catalytic convertors are required on diesels in the US but I am sure that they do some good for the atomsphere even though there is not much unburned HC's in diesel exhaust compared to gassers.
As far as the catalytic convertor is concerned, if the VW is small enough to create a bottleneck in the flow, a trashed cat from a GM, FORD, etc. V-8 could be installed and it would work good and for sure have more than enough flow for whatever the TDI engine could put out. The idea being, if it is good enough for a V-8 exhaust flow, it a HAS to be good enough for a puny 1.9L TDI.
My A4 turbo hookup is similar to your A3's although the turbo itself is integrated on mine whilst added on the manifold on yours. The exhaust downpipe appears similar back to the cat. I will get under there and measure it with a caliper during the installation to check it out closer. It does look pretty heavy duty, being solid stainless steel throughout, really a first class piece.
I am looking forward to that Techtonics Exhaust for some more flow and less back pressure to assist my turbo flow characteristics somewhat. As far as I know, my setup does not have a resonator in it, but if it does, I will remove that too. For one it will sound alot better.
Soon, when I crank this baby up on a dark, cold, foggy morning, the nearest neighbors (about 1/2 mile away) will think that I am cranking up my Massey Ferguson tractor, without the resonator, they may think that the locomotive at the train station about three miles away is cranking up!!!!
That awesome diesel manages to shake the ground all the way over to our farm!

Wait until these poor hapless chaps hear the sounds of my 1.9L VW TDI mit Wett mit Garrett VNT15 turbo hit the road wide open, their mouths will drop open in awe. Hope I do not interfere with the Hoot Owls in the trees around the farm, they may not be able to handle hearing that turbo spool up to 130,000 rpm sending millions of soundwaves out the Borla faster than the speed of sound.

The TDI does indeed use a cat, but it is formulated differently owing to the fact that the equivalence ratio changes over a wide range in diesels in the course of normal operation.

In gas engines, in order for the cat to work most efficiently, the fuel-air mixture MUST be regulated over a VERY narrow range near stoichiometric. That's what the O2 sensor's primary role is here.

As you pointed out, Diesels emit less CO and HC than gas engines, but more NOx. Because Diesel exhaust always has excess air, chemical equilibrium dynamics suggests that reduction of NOx to its component N2 and O2 is difficult. The function of the catalyst in the TDI is to reduce all three of these pollutants, plus carbon-based soot (soot has two main forms). It does this by two different chambers with different formulations. One is an oxidizing part that deals with the HC, CO and soot, while the reducing part deals with NOx.

In short, what I'm saying is that while you may pass visual inspection with replacing the cat with some other part, it may not likely work AT ALL at what it's supposed to do, plus it may become plugged with with soot in no time.

And don't be fooled into thinking a larger physical size from a GM unit will flow any better or be any more effective. Fact is, the VW units flow EXTREMELY well. This has been proven by publications, and by the fact that HP is not significantly affected from removing the cat vis-a-vis leaving it in. Darrel Vittone from Techtonics has vouched for this for a long time in mags like VW & Porsche and European Car, and I've spoken with him personally.

I personally am not replacing my OEM cat on the TDI and was never planning to, since as you mentioned the VW OEM unit is excellent and could not be inhibiting the flow to any great extent unless the motor was set up for full race. I agree wholeheartedly with your assessment of the facts pointed out in your post. I am just changing out cat-back only since I am never going to be a full race set-up. This should decrease backpressure a couple of pounds and correspondingly increase turbo exhaust flow too. Every little bit helps, and if I ever achieve further boost pressure increases as planned, the Techtonics unit will be a further plus!
Thanks for the info, Dave!

I thought I read a post a long time ago that mentioned that the cat ignites diesel fuel in the cat to help heat it up and improve the output levels of chemicals. If this is the case, how do you rememdy the issue of the fuel supply line and no cat?
I have never really looked at the cat up close I just seem to remember something strange like that being posted.

Hey SkyPup,
Stop the madness. Everytime I convince myself to spend the designated bit of play-money on something one of you guys post a message like this and get me thinking otherwise. My fellow air cooled VW friends
(THING owners) are calling the TDI group the "Dark Side" since I'm spending more time tinkering and playing with my Jetta than my '73 THING.
What was once a purchase to merely get me to and from work is becoming a focus of much attention lately. All jokes aside, when you get the full flow exhaust installed I'd love to see and hear it. I'm down the road from you in the Tampa area. Give some thought to attending the Dade City Bug Jam / VW show on November 14th. It's a very good show for those who have never attended. While the big numbers are naturally air cooled there are also many classes for water cooled.
Given a bit of time to recover from the recent stereo upgrade I will be adding a Power Box and have a line on a local shop for a Dyno test. Maybe this would be a good chance to head to head test the two most popular methods of hot-rodding these wonderful engines.

Driver, thanks for the nice note, indeed the TDI Performance people are the "DARK SIDE" since very few ever enter these hallowed halls, most just tremble at the thought of a souped up diesel powered VW TDI, many just soil their undies when the vision occurs in their minds eye. We are here to cure those symptoms of either NO TDI or STOCK TDI. Can you imagine that the 1.9L VW TDI is the ONLY diesel powered passenger car for sale in the United States of America during the millenium? Everyone who owns and operates a TDI is in an extremely small minority in this county, those you have a HOPPED UP TDI are in an even smaller minority. It is our responsibility to get the word out to the masses that the future is here right beneath our noses, I can smell those TDI fumes now.
Nov 14th I will be harvesting my vension for the fall after I split up some wood for the fireplace, however, that is a nice invite and would appreciate if you post some more info regarding the outcome, possibly a few pics would be nice to send to Fred to post too. Some good TDI folks up in Atlanta are getting ready to test dyno their WETTED TDI's soon and post results of same (Gary!), that should provide some more fuel to the fire.
VW TDI ENHANCED -&gt; SIMPLY STUNNING

Yes, I had forgotten for a moment that the citizens of the great state of California had been Californicated from behind once again.
LOL Hey, we better still be nice to them since alot of good VW Tuners still operate within the border of that state.

Is the resonator the muffler closer to the engine? How much louder does this make the TDI? Will this make the noise of the turbo spooling up louder. I love that sound and I try to make sure every rice rocket I see hears it.

If I am blessed, I will have the Techtonics system by this Friday but I am not holding my breath since it is a long 3,000+ mile UPS ride from Oregon to Florida (hope no natural disaster occurs during the shipment - floods, earthquakes, 50 car pile up on the Interstate, etc.). It should be a piece of cake install, and I will be exicted to hear the sweet sound of that Wett TDI talking to me through the turbocharged exhaust for sure!
Rest assured that FRED'S TDI PERFORMANCE PAGE will be the first recipient of the news of my miraculous discovery in horsepower hop up on the techno rad Jetta. If I don't receive it before this weekend though, it may be the week after as I am busy baling horse hay on the farm to put up in the barn before winter. Can't let those horses down for a few more horses on the TDI!!!